Pixels per inch or ppi.

Depends of the number of pixels per centimetres or inch (Ppi- pixel per inch).

no ,dots are dots and pixels measure how big a picture is.

There are 44,521 pixels per square inch on a third generation iPad.

The number of pixels per inch on a widescreen television will also depend on the type of television it is. For example an HDTV television will have more pixels per inch to provide better picture quality. An HDTV would run at approximately 1080 pixels per inch.